The wide use of antibacterial agents such as antibiotics in animal industry has greatly promoted the development of breeding and animal industries. At present, more than 95% of premix products have antibacterial agents added therein. However, this addition also suffers from increasingly significant disadvantages in that, products of the animal industry have severe drug residues that directly harm the health of human bodies; the abuse of antibiotics causes pathogenic germs to develop drug resistance, leading to diffusion and spread of drug-resistant strains; at the same time, dysbacteriosis is caused in animal bodies, decreasing the animal immunity, deteriorating the breeding environment, and increasing diseases; and a series of severe problems such as endogenous infection as well as superinfection and cross-infection are initiated in animals. Since 2006, The European Union has began to completely prohibit the addition of antibiotics into feed, and reduce or prohibit the addition of antibacterial agents into feed. The United States also beganto prohibit the use of antibiotics in feed. Currently, universal attentions from various countries around the world have been paid to the standardization and reduction of use of antibacterial agents in breeding processes, and the development of safe and green feed additives as surrogates thereof.
The lactobacillus microecological feed additive is an important surrogate for antibacterial agents. Lactobacillus is one of outstanding representatives of beneficial bacteria in the enteric normal flora, and has important physiologic and health-care functions in that, it can antagonize pathogenic microorganism, and adjust the microflora balance of digestive tracts in animals; It can activate the immune system, enhance immunity, and prevent the occurrence of various diseases and adverse reactions; it can inhibit the occurrence of tumors, and protect the animal health; it can synthesize nutritional substances, produce digestive enzymes, increase activity of the digestive enzymes in animals, ameliorate the metabolism of vitamins, neutralize enterotoxins, and reduce the production of harmful substances such as amine and ammonia; and the like. However, lactobacillus forms no spores in the growth process, has poor stress resistance, and is very sensitive to external environment, for example, oxygen, moisture, elevated temperature, mechanical squeeze, heat shock and gastric acid, so that the number of viable bacteria is hard to be ensured effectively in practical use. Therefore, how to screen out excellent lactobacillus strains and prolong activity of commercial products thereof has always been a research and development emphasis of lactobacillus manufacturers over the world.
The capsule technique is one of the most effective and practical method for protecting the bacterial vitality. By encapsulation of lactobacillus, bacterial bodies can be separated from adverse external environment, in order to protect against impairment from microelements in the feed, and alleviate the influences from temperature and pressure in the granulating process. By the formation of solid particles, uniform distribution in the premix is favored, and storage and transportation are favored as well. By the employment of an enteric wall material, it can be further ensured that as many bacterial bodies as possible reach the intestinal tract, to allow the bacteria to actually exert health-care and therapeutic efficacy.
For example, Patent CN1613455 disclosed a probiotic microcapsule coated with a three-layer protection layer; and Patent CN1569043 disclosed a lactobacillus microcapsule produced by spray coating in a fluidized bed by employing sodium alginate and calcium chloride as the wall materials. The above patents increase the survival rates of probiotics or lactobacilli to certain extents. However, inevitably, in CN1613455, the temperature of hydrogenated oil and fat exceeding 55° C. may cause damage to lactobacilli inside the core material, and at the same time, the outer controlled release coating material allows the lactobacilli to fail to quickly release in the intestinal tract, thus a part of the lactobacilli will be discharged out of the body, and availability of the lactobacilli is reduced. In CN1569043, sodium alginate is employed as the wall material, which is frequently used in the coating of a microcapsule at present. However, sodium alginate itself has poor moisture holding capacity, and microcapsule gel coated with sodium alginate is liable to water loss, hardening, and cracking. In addition, microcapsules coated with sodium alginate are intolerant to gastric acid, and have poor capacity of passing through stomach. A patent named A Method for Preparing A Lactobacillus Powder Containing Multi-Layer Microcapsule Lactobacilli, with a patent application number of 201310743621.4, is characterized in that, 20 to 30 parts of marine fishskin collagen oligopeptide powder, 5 to 20 parts of citric acid, and 40 to 50 parts of multi-layer microcapsule lactobacillus powder are mixed and stirred. An invention named Lactobacillus Microcapsule And Preparation Method and Use Thereof, with an application number of 200810135259.1, also discloses a lactobacillus microcapsule and preparation methods and use thereof. The lactobacillus microcapsule consists of an outer wall material, a cryoprotectant and lactobacilli.
In summary, the existing microcapsule coating technique either causes a greater damaging effect on lactobacilli during its implementation process, or produces a microcapsule that has poor tolerance to the stomach environment, which are all unfavorable to the industrialization and application of microcapsule products.